Dispersants keep insolubles within the oil suspension, thus preventing sludge flocculation and precipitation. Suitable dispersants include, for example, dispersants of the ash-producing and ashless type. Derivatized olefinic polymers have been used as ashless dispersants and multifunctional viscosity index improvers in lubricant and fuel compositions.
In the lubricating oil sector, these are generally referred to as ashless dispersants, and, in the case of the polybutylphenols, as Mannich dispersants. The purpose of these dispersants is to keep in suspension oil-insoluble combustion residues, and thereby prevent deposits on metal surfaces, thickening of the oil and sludge deposits in the engine and to avoid corrosive wear by neutralizing acidic combustion products.
In the motor fuel sector, the secondary products are generally referred to as carburetor or valve detergents. Their task is to free the entire intake system from deposits, to prevent further deposits and to protect the system from corrosion.
Functionalized olefinic polymers are particularly useful as additives in fuels and lubricating oils. Fuels include normally liquid petroleum fuels such as middle distillates boiling from 65.degree. C. to 430.degree. C., including kerosene, diesel fuels, home heating oil, jet fuels, etc. A concentration of the additives in the fuel is in the range of typically from 0.0001 to 0.5, and preferably from 0.005 to 0.15 wt. %, based on the total weight of the composition.
Additives may also be used in lubricating oil compositions which employ a base oil in which the additives are dissolved or dispersed therein. Such base oils may be natural or synthetic. Base oils suitable for use in preparing the lubricating oil compositions include those conventionally employed as crankcase lubricating oils for spark-ignited and compression-ignited internal combustion engines, such as automobile and truck engines, marine and railroad diesel engines, and the like. Advantageous results are also achieved by employing such additives in base oils conventionally employed in and/or adapted for use as power transmitting fluids, universal tractor fluids and hydraulic fluids, heavy duty hydraulic fluids, power steering fluids and the like. Gear lubricants, industrial oils, pump oils and other lubricating oil compositions can also benefit from the incorporation therein of the additives of the present invention.
Functional polymers having a number average molecular weight (M.sub.n) in the range of 700-5,000 have been used as intermediates in the synthesis of dispersants (i.e., additives) for fuel and lubrication applications. The most common functional groups are cyclic anhydrides, carboxylic acids, and phenols. These groups could be further elaborated to imides, and amides and Mannich based products with a variety of polyamines.
A conventional method of preparing polymeric acids and anhydrides generally involves pericyclic reactions of .alpha.,.beta.-unsaturated carbonyl compounds with polymeric olefins either directly or in the presence of chlorine. These reactions often lead to the incorporation of more than one functional group per polymer.
The cobalt or rhodium-mediated hydroformylation of olefin polymers has been utilized to a more limited extent to prepare alcohols and aldehydes. Use of the hydroformylation process results in the consumption of the carbon--carbon double bond during the reaction, thereby introducing only one functional group per polymer in the absence of diene comonomers.
U.S. Pat. No. 3,311,598 (Mertzweiller et al.) discloses the hydroformylation of a multi-olefinic hydrocarbon polymer with carbon monoxide, and hydrogen, in the presence of catalyst containing a transition metal selected from Group VIII of the Periodic Chart, to form hydroxylated (--CH.sub.2 OH) and/or carbonyl (--CHO) derivatives of the polymer. The polymer is preferably either a polymer of polybutadiene, polycyclopentadiene, polyisoprene, and mixtures thereof, a butadiene-styrene copolymer, a pentadiene-styrene copolymer, or an isoprene-styrene copolymer.
Polyisobutene derivatives (e.g., polyisobutyl-amines) have frequently been described in the literature and are used worldwide on a large scale as lubricant and motor fuel additives. The intermediates for the preparation of such additives are polybutenyl chloride, polybutenylsuccinic anhydride and polybutylphenols. See U.S. Pat. No. 4,859,210 (Franz et al.); U.S. Pat. No. 4,832,702 (Kummer et al.); and WO-A 90/05711.
The efficiency of the hydroformylation reaction as applied to polyisobutylene (PIB) varies with the type of polymer, and conversions range from 59-81% with the most reactive PIB's available (see U.S. Pat. No. 4,832,702). It would be highly desirable to increase the rate of conversion in the hydroformylation of polyolefins to as close to 100% as is technically feasible.
The present inventors have discovered that olefinic polymers prepared with a metallocene catalyst are especially suited for use in the hydroformylation process and synthesis of unique polymeric alcohols and aldehydes in substantially higher yields than even the reactive PIB's on an equal weight percent basis.
Unfortunately, hydroformylation has been observed to produce undesirable side products. Attempts to produce polymer aldehyde in high yield from metallocene catalyzed olefinic polymers and vinylidene containing models has shown that 15-20% of the olefin is typically hydrogenated using cobalt catalyst; furthermore, there is a conversion-dependent loss of aldehyde to alcohol which also limits the yield of aldehyde available for reductive amination. The present inventors have also discovered that amine derivatives may be prepared in substantially higher yields by subjecting the metallocene-catalyzed olefinic polymers to aminomethylation in a single step rather than the conventional two step process of hydroformylation followed by reductive amination.